hydraulic assembly basics - project...
TRANSCRIPT
Hydraulic Assembly Basics
Gui Cavalcanti
5/8/2012
Overview
• Setup
• Fitting Types
• Hose Sizing
• Assembly Techniques
Setup
• Assume everything will get coated in
hydraulic oil. Everything.
– Drop cloths on all tables and surfaces
– Absorbent media available at all times
– Cleaning station to degrease tools
• Wear gloves at all times, wash hands
immediately after working with oil
Fitting Types
Fitting Types - JIC
Fitting Types - JIC
• Sealing surface:
– 37 degree flare on nose of male fittings
• Tensioning mechanism:
– Free-swiveling, floating hex nuts on straight threads
• Pros:
– Easy to assemble
– Widely available
– New industry standard
• Cons
– Easy to not tighten enough
Fitting Types - NPT
Fitting Types - NPT
• Sealing surface:
– Tapered screw with seal lubricant
• Tensioning mechanism:
– Non-swiveling or swiveling tapered screw
• Pros:
– …
• Cons
– Almost always leak
– Difficult to assemble
– Easy to screw up
Fitting Types - ORB
Fitting Types - ORB
• Sealing surface:
– O-Ring touching down on machined surface
• Tensioning mechanism:
– Straight non-swiveling thread
• Pros:
– Easy to assemble
– Widely available
– Very robust
• Cons
– O-Ring tearing if mishandled
Fitting Types - Flange Mount
Fitting Types - Flange Mount
• Sealing surface:
– O-Ring touching down on machined surface
• Tensioning mechanism:
– Bolt pattern
• Pros:
– Easy to assemble
– Widely available
– Very robust
• Cons
– O-Ring tearing if mishandled
Hose Sizing
Hose Sizing
• Hoses are sized by “Dash Number”
• Dash number is hose inner diameter in
inches:
– I.D. = Dash Number / 16
– “Dash 8” = 0.5” I.D.
Hose Sizing
• Draw a line
between desired
flow rate and
minimum or
maximum flow
velocities for your
type of hydraulic
path
Hose Sizing
• Pressure to
individual valve:
– 6 GPM
– Pressure line
– Dash 5-6
Hose Sizing
• Return from
individual valve:
– 6 GPM
– Return line
– Dash 8
Hose Sizing
• Main pressure line
to system:
– 35 GPM
– Pressure line
– Dash 12-16
Hose Sizing
• Low pressure inlet
to hydraulic pump:
– 35 GPM
– Suction line
– Dash 24-30
Assembly Techniques
Basics
• Essentials:
– Hydraulic oil acts like a grit/dust magnet
– Grit/dust destroys hydraulic systems
– All surfaces must be cleaned and oiled before
assembly
• Set up in as clean an environment as possible
• Never leave hydraulic oil or cavities uncovered
for any longer than necessary
Components
• All components must be filled
with hydraulic oil before being
attached to a system
– Fill a small squeeze bottle with
hydraulic fluid, use it to fill
components as much as
possible before assembly
• Consequence if not followed:
pumps, cylinders, and valves
die or misbehave
Bleeding
• Traditional hydraulic systems have some way of
“bleeding” – removing air from hydraulic lines as
much as possible
• Open circuit systems suffer less than closed
circuit systems
• We have no effective way to do that right now;
therefore, caution is called for
• Fill everything as much as possible
Fittings
• All fittings must be wetted
– Threaded surfaces coated in hydraulic oil before
assembly to lubricate tightening procedure
• NPT fittings must be coated in seal lube
– ABSOLUTELY NO TEFLON TAPE
– No seal lube for any other type of fitting
• Fittings should be tightened as much as
humanly possible